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1.
I.IntroductionTheprob1cmofsuppressingstrongpointinterferencesourceisavcryimportantthesisinsonardesign.Fortheana1ogsonar,thesolutionofthisprob1emisquitedifficu1t.Untilthedevelopmentofdigitalsonar,thereissomerescarchreportsaboutsuppressingstrongpointin-terferencesource.Theear1ierworkin1969,dedicatcdbyV.C.Anderson,istheconccptofDICANNE(DigitalInterfcrcnceCance1lingAdaptiveNu1lNetworkEquipment)['l.Thisisadoublecompensatormulti-bcamsystcm.Oneisusedtoformintcrfercncebeamandanothcrisusedtofor…  相似文献   

2.
I.IntroductionTherearetwowaysofcvaluatingconcertha1lacoustics.Oneistoevaluatetheacousticalqualityofaconcertha11ateachlistener'spositionrespectively,andtheotheristoevaluatetheacousticalqua1ityofaha1lasawho1e.Bothwaysarebasica1lysimilar.Howcvcr,sincesomcob-icchveparametersmayhavedifTerentvalucsatdifferentpositions,onemustdcfinesuitab1ein-dicestodescribetheseparameters(e.g.meanva1ucsorothers),sothatacomparisonbetweenha1lsbecomcspossib1e,Thispaperdea1swiththelattereva1uationbyusingfuzZysettheory…  相似文献   

3.
I.IntroductionTheinvcrseprob1cmofsoundscattcringisinterestingtou1trasonicdiagnosis,identificationofanundcrwatcrtargct,speechsynthesisctc.UsingthismethodDucheneandTabbara[1.21.studiedtheu1trasonicdiagnosisofab1oodvessel.Inthispaperweusedasoft-tubetosimulateabloodvesselanddeaIswiththeu1trasonicdiagnosisofthesofc-tube.Invcrsescatteringprob1emdcterminingatubeparamctcrswasgivcn.Agcomctrica1acousticsmethodwasuscdindescribingthescattcrcdfield.Fivcparametcrsofthctubcwercrcconstructcd.Therelativcdc-…  相似文献   

4.
I.IntroductionFluteisanancientmusicinstrument.Itsprincipa1structureisasegmentofcircu1arpipewithaseriesofaperturesonthewa11.Amongtheseapertures,oneisca11edblowingapertureandothersarecalledtuningapertures.Duringperformance,thep1ayerb1owsbythecdgeofblowingapertureandcontro1sthetuningapertureswithcertainfingeringtoexcitedifferentpuretones.Forapopularflute,onetcrmina1ofthcfluteisopenandtheothcrisclosedwithapiston.Thetuningaperturesaresett1edneartotheopenterminalandtheblowingapertureneartotheclose…  相似文献   

5.
I.IntroductionInordcrtocfficlcntlyprcdictandcontro1thenoiseinindustria1enclosurcs,manypeoplehavestudicdmathmodclsforsoundpropagationinindustria1enclosurcs.Butsofar,thereisnosatisfactoryrcsult.Inthepast,a1mostal1studieswcrercstrictedtoidealemptyindustrialcnc1osurcs,andonlyafewofthcm['-']concerncdtheinfluenceofobstac1cswithinthemodel.Thcscmodc1strcattheobstac1eeffcctsbythemethod-ofimagesandcanonIybeusedtoregu-larhexahcdronroomswhcreobstaclcsareassumedtobedistributesuniformIy.Ondet'sartic1el'],…  相似文献   

6.
I.IntroductionUptonowtheultrasonicpu1seechotechniquehasbeenwide1yusedinthefieldofnon-destructivetesting.Toachievehightargetreso1ution,narrowpu1seshou1dbeadoptcd.Butthiswill1imitthetransmitpowerandthcdetectab1erange,whichisveryboportantcspecia1lyinthemediumwithstrongacousticattenuation.Itmeansthatthetargetresolutionanddetcctablerangehavccontradictorydcmands.Thcrcforethepulsccompressionandcorre1ationtechniqucdeve1opedinradarsystemhavebeenintroducedintotheultrasonicNDTandsomeprogresseshavebeenp…  相似文献   

7.
I.IntroductionThedigita1operationins0narsystembringsagreatadvantageinbeamforming.Itispos-sib1etorealizesomcalg0rithmsindigita1technique,whichisusua11yhardtoorimpossib1etoAnp1ementintraditiona1ana1ogues0nar.Asanexamp1e,ageometrygraphofcirclearrayisil-1ustratedinFig,1.Thetotalnumber0farraye1ementisN.Therearetwokindsofbeam.TheA-c1assbeamconsistsof2M-le1ements,thesteeringdirectionisjustlocatedintheposi-honofoneofthearrayelement;TheB-classbeamconsistsof2Me1ementsandthesteeringdirectionisinthem…  相似文献   

8.
I.IntroductionApostbeamformernoisecancel1erisasing1e-channeladaptiveprocessorinbeamspace['l.Ithasnotonlysimplerstructure,buta1sobetterpropertiesthane1ementspaceprocessorinimp1ementation.L.C.GodaraandA.Conto1ihavestudiedthesignaltonoiseratioofthebroadbandPIC[1].Theauthorshavesolvedtheprob1emofapplicationconditionsofnarrowbandPIC['],andproposedthatRMGSEFa1gorithmistheoptimuma1gorithminthenarrowbandPICadaptiveprocessing['1.Atpresent,thepfob1emofadaptivecance11ingofbroadbandtowing-shipnoi…  相似文献   

9.
I.IntroductionInmanycasesthecontinuityofsoundpropagationwithinatubeisbrokenbyaperturesonthetubewallsuchastoneholesonthemainboreofwoodwindmusicalinstruments,rectangularsound-windowofChineseinstrumentshengetc.Thediscontinuityhaseffectonwavccncoun-tCringit.Keefestudicdasing1etoneholeofwoodwindinstrumentandrepresenteditbyaT-sectionequiva1entcirc.it[11.Inthispaper,theapertureontubewa1lisstudiedfromdifferentpointofview,a1thoughtheGreen'sfunctionmethodisalsousedinthetheoreticalana1ysis.Moresimp1er…  相似文献   

10.
1.IntroductionThemaximumoutputofatransformeramplitudeislimitedbythefatigueofthema-tCrialusedlll.Ifthesurfaceshearstressofatorsionaltransformer,T,isuniformalongtheaxis,inotherwords,themaximumpointofsurfaccshearstrcssisincxistent,ti.ea1lowab1coutputpowcrofthetorsionaltransformerwillenormouslyincrease.Insomecasesinwhichveryhigh-intcnsitytorsiona1ultrasonicpowerisrequired,theywil1benecessaries.Forthispurpose,wederivedthenewtypeoftorsionalangletransformer-quartcr-wavelcngthhypcrbolicsccanttaper.T…  相似文献   

11.
The current main approach to reconstruct and predict the acoustic field of a planar source is Near-field Acoustical Holography (NAH) based on FFT. But this method has some disadvantages such as wraparound error and edge Gibbs phenomena which will contaminate the results badly. A planar NAH based on equivalent source approach is developed, which has no wraparound error and edge Gibbs phenomena, and it is beneficial for engineering application. The experimental results of acoustic radiation generated by a point-driven plate with clamped boundaries validate the correctness and availability of the method.  相似文献   

12.
高超声速飞行器前缘疏导式热防护结构的实验研究   总被引:2,自引:0,他引:2       下载免费PDF全文
孙健  刘伟强 《物理学报》2014,63(9):94401-094401
针对高超声速飞行器前缘疏导式防热结构的特点,设计前缘内嵌高导热率材料结构和一体化层板热管结构两类对比实验,用于验证前缘疏导式防热结构的可行性.利用球形短弧氙灯作为辐射热源模拟气动加热,分别对钢质前缘、内嵌铜材料的钢质前缘和一体化层板式热管前缘进行加热,测量前缘驻点区域和尾部翼面区域的温度变化.实验结果表明:内嵌高导热率材料的前缘疏导结构能够降低头部驻点区的温度,提高尾部低温区的温度,实现对前缘结构的热防护;以蒸馏水作为工质一体化层板式热管前缘结构,在较低热流条件下也能够实现对前缘驻点区的疏导式热防护,但在较高热流条件下,由于水蒸气压力过大使得层板式前缘结构发生破坏,体现出热管内部工作介质对结构防热效果和应用范围都起到的关键作用.  相似文献   

13.
K. Hosotani 《显形杂志》2006,9(4):427-435
The warm ocean water filaments are emanated periodically in winter from the meandering Kuroshio Current at the East China Sea. They bring the intermittent warm ocean water intrusion into the Kagoshima Bay well known as ‘Kyucho’ phenomenon. From the satellite SST images, the warm water intrusion is also observed at the Fukiage Seashore. In addition to the warm water intrusions, the cold-water mass at the Osumi Strait is observed. In this study, the numerical analysis is performed to understand these phenomena. A density current is calculated by a multi-leveled finite difference method (FDM). Then, particle trajectories are calculated by the Lagrangian particle tracking method by using the previous current result. Particles are dealt with as passive tracers to be a model of plankton and hyponeuston (i.e. larva, eggs or seeds) of an open sea. Calculated results of the warm water mass show similar features of the SST images, i.e. the warm water intrusions into the bay and the cold-water mass generation. The warm water intrusion occurs when it reaches the mouth of the bay or the edge of the coast. The cold-water mass is concerned with a horizontal vortex shed from the edge of the cape. The cold-water mass is produced in a stagnation region by a horizontal vortex rather than upwelling from the deep ocean. The particle trajectories have a tendency to pile up in the bay and a stagnation region behind of the peninsula. These results supply the fundamental knowledge that contributes to biological problems at the south of Kyushu in winter adequately.  相似文献   

14.
陈赵江  张淑仪  郑凯 《物理学报》2010,59(6):4071-4083
对高功率超声脉冲作用下金属板中的超谐波、次谐波、准次谐波以及混沌等非线性振动现象进行了实验和理论研究.在实验中,高功率超声换能器产生脉冲调制的高频振动激励金属板产生非线性振动,利用激光测振技术测量不同尺寸和不同固定方式下金属板复杂的非线性振动情况,并对其进行了时序分析、频谱分析以及相空间分析.根据实验条件,提出包含非线性接触阻尼的振动-碰撞动力学模型,用以研究强超声振动-碰撞作用下的板非线性振动机制,并进行了相应的理论计算.计算结果表明,超声换能器的变幅杆与金属板之间的间歇性高频碰撞作用是金属板强非线性振 关键词: 非线性板振动 强超声脉冲激发 振动-碰撞动力学  相似文献   

15.
介绍两种实现激光自准直的方法和实验,阶梯相移片法的特点在于巧妙地利用相移片对入射光进行调制,实现高精度激光自准直和角度的测量;微点相移片法是比较入射光与反射光通过相移点的衍射图形,达到激光自准直的目的。用夫琅和费标量衍射量论分析和计算了激光经过两各片调制后的光能分布,并对制作公差进行了讨论。  相似文献   

16.
A fundamental study aimed at investigating the stabilization characteristics of edge flames established in the near-wake of two merging streams, one containing fuel and the other oxidizer, is presented, with the main focus placed on the effects of the thermal interaction between the flame and the splitter plate. To this end, a diffusive-thermal model characterized by constant gas density and transport coefficients is used for conditions at which flame liftoff is likely to occur. It is assumed that the incoming streams are of equal strain rates, that the fuel and oxidizer are supplied in stoichiometric proportion, and that the mass diffusivities of the reactants are equal, such that the resulting combustion field is symmetric with respect to the centerline extending from the splitter plate. The results indicate that the plate has a negligible effect on the edge flame unless the tip of the plate intrudes into the preheat zone of the curved premixed flame segment forming the edge flame. In an overall adiabatic system, the heat conducted from the flame to the plate is completely recirculated back to the reactants via the lateral surfaces of the plate, thus supporting an excess enthalpy flame in the near-wake. The average output heat flux, defined as the total heat output through the lateral surfaces of the plate divided by the characteristic length associated with the temperature variation along the plate, is identified as an appropriate measure to characterize the heat recirculation efficiency.  相似文献   

17.
In this paper a laboratory-scale model for prediction of the voltage–current characteristics of wire–plate electrostatic precipitators under clean air conditions is presented and experimentally validated. The model investigates the effect of electrode configurations, wire diameter, spacing between wire electrodes, number of discharge wires and distance between collecting plates that on voltage–current characteristic of wire–plate electrostatic precipitators. Also, this paper presents a simulation model, based on the Finite Difference Method (FDM), to simulate electric conditions of wire–plate electrostatic precipitators under clean air conditions. The experimental results of some models are compared with those obtained from the simulation models.  相似文献   

18.
黄坤  殷雅俊  吴继业 《物理学报》2014,63(15):156201-156201
基于实验得到的非线性本构关系和板理论,本文建立了包含三次及五次非线性项的单层石墨烯片的板动力学模型.针对四边简支矩形板,使用Ritz法研究了在板中点作用集中力时的静力弯曲,以及边界均匀受力时的静力屈曲问题.结果显示,基于非线性本构关系的板模型能很好的描述单层石墨烯片的力学行为,而且模型中的五次非线性项对结构的弯曲变形有显著影响.  相似文献   

19.
This paper deals with a study of the conversion of a Lamb wave at the loaded edge of a plate. An experimental study is performed to know the interaction of surface waves with a viscoelastic material. A Lamb wave is generated by a wedge. At the end of the plate, this wave gives rise to several reflected waves. A first study makes it possible qualitatively to know the Lamb modes present in reflection. Secondly, conversion phenomena are studied to know if surface waves are sensitive to evolution in the time of the viscoelastic material structure. The selected material is a sol-gel containing silica.  相似文献   

20.
王玉成  刘雄军  陈澍 《物理学报》2019,68(4):40301-040301
准周期晶格在冷原子领域被广泛研究,它使得人们可以在一维或者二维系统里研究扩展到安德森局域的转变. 2008年, Inguscio研究组在冷原子系统里制备了一维准周期晶格,并观测到了安德森局域化现象,这极大地推动了准周期系统的理论和实验研究.后来, Bloch研究组在制备的一维和二维准周期晶格中都观测到了多体局域的现象.最近,他们还在准周期晶格中成功观测到迁移率边以及存在迁移率边的系统的多体局域现象.这些冷原子实验推动了多体局域以及迁移率边等方向的研究.准周期晶格已经成为一个平台,它对很多物理现象的影响正在被广泛研究,并可以尝试在冷原子实验中观测到这种影响.本文结合作者的一些相关工作,对一维准周期晶格一些近期的研究进行了简要综述,介绍了一些相关的重要的冷原子实验,讨论了准周期晶格的一些重要性质,以及它对一些物理现象(比如拓扑态)的影响.  相似文献   

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